The present invention relates to novel suspensions and their preparation and use.
The demands placed on modem lacquer binders include high hardness with at the same time high elasticity, good weather resistance and chemical resistance as well as a possibly low emission of volatile organic substances during application and curing. Meanwhile, water-based organic binders are highly developed; lacquer systems based on acrylate, polyester and polyurethane are used in the lacquering of wood, for example, in furniture lacquering as well as metals and plastics, for example, in the lacquering of automobiles, railway vehicles, ships and in industrial lacquering. Aqueous binders based on polyorganosilicones are also known. Because of their chemical structure, silicones substituted with methyl groups in particular have an outstanding weather resistance and water repellency. Their water repellency in particular renders them efficient constituents of paints, for example, on the exteriors of buildings.
Multifunctional carbosilanes, which are described in DE-A 19,711,650 and DE-A 19,603,241, are also suitable coating materials. Such compounds combine the hardness and elasticity of high-quality organic lacquer binders with the high weather resistance and low tendency to yellowing of methylsilicones. But the processing of multifunctional carbosilanes is subject to difficulties. Thus it has not been possible to use them as binders in aqueous lacquer formulations. Moreover, prior to application these binders have had to be aged in solvent-containing catalyst formulations and then processed within a certain period of time.
The object of the present invention was to provide aqueous suspensions (dispersions or emulsions) which are based on these carbosilanes and are stable in storage.
It has now been found that the object stated above could be achieved using suspensions (emulsions or dispersions) according to the invention, when these contain particular siloxanes or silanes, emulsifiers, and optionally conventional additives and auxiliary substances in particular proportions in water. This is surprising, as those skilled in the art would have to assume that these multifunctional carbosilanes or siloxanes in water would become unusable in time, owing to progressive hydrolysis and condensation reactions. The suspensions according to the invention nevertheless exhibit a very high stability in storage.
For the purpose of this invention, the term "suspensions" includes emulsions as well as dispersions.